1. Field of the Invention
The present invention relates to medical devices used in needle localization procedures for locating lesions within the body. More specifically, the field of the invention is that of devices used to localize small nonpalpable lesions.
2. Description of the Related Art
To detect small nonpalpable lesions within the breast, women have mammographies performed periodically. Mammography involves the radiographic examination of the breast for nonpalpable lesions, so that the lesions, which are normally undetectable by sight or feel, may be visually identified on the radiogram or x-ray. The lesion areas may include cancerous or other diseased tissue which should be removed. Early detection and removal of cancerous lesions can greatly improve a patient's ability to avoid life or limb threatening complications. Although many lesions are ultimately determined to be benign, it is generally recommended that a woman have frequent mammographies as a precaution against cancerous growths.
In current practice, if a lesion is detected in the breast, a guidewire, needle, or similar device is placed in the breast tissue as close as possible to the lesion so that it may be identified and located during surgery. The tissue which has the lesion is located in relation to the position of the needle within the body tissue. First, the lesion must be detected by mammography. Second, assuming a lesion is detected, a second mammogram is taken with the needle positioned in the breast tissue. If the needle is sufficiently close to the lesion in both the craniocaudal and mediolateral mammograms, then the patient is prepared for surgery. If the needle is not positioned correctly, this procedure is repeated until the lesion is appropriately positioned to locate the lesion.
Although the needle itself could be used for location of the lesion, generally the needle includes a hollow axial center for the introduction of marking material to identify the tissue. Two different methods are used to identify the tissue, which can be used separately or jointly. The first method uses a guidewire which is introduced through the needle and anchored into the breast tissue. The second method uses a tissue staining dye which is injected by the needle into the tissue around the lesion. Later in the day, surgery is performed wherein a cylinder of tissue around the position of the needle is removed. The cylinder of tissue to be removed is determined by the position of the needle, guidewire, or dyed tissue within the breast. However, because of the possibility that body tissue has shifted between the taking of the mammogram and the surgical procedure, the size and extent of the cylinder of tissue being removed is relatively large to minimize the chance of missing a significant portion of the lesion tissue.
A difficulty in the prior art procedures involves the depth of the lesion tissue in the breast. The location of tissue within the breast is altered when positioned within the mammography machine so that by the time of surgery, the lesion tissue frequently has moved to a different position. Also, it is difficult to determine the exact location of the lesion along the axial length of the needle from the two views of the mammogram.
To compensate for the shifting and movement of tissue and the inexact determination of the location of the lesion, a relatively large cylindrically shaped portion of tissue is removed during surgery to ensure that the entire lesion is removed. However, this cylindrically shaped portion of tissue is often much more tissue than is necessary which results in the undesirable removal of healthy tissue. Occasionally, the lesion tissue is not completely removed because of the inaccuracies in determining location of the lesion tissue. Further, for some patients who may have several lesions requiring removal, a substantial amount of healthy tissue may be undesirably removed.
What is needed is a device and procedure for the identification of lesion tissue within the breast which allows the accurate removal of the lesion tissue and a minimal amount of healthy tissue.